Photographic tracing cloth



Feb. 23, 1954 Q F, SMlTH 2,670,288

PHOTOGRAPHIC TRACING CLOTH Filed NOV. 30, 1951 I6 EMUL SION 15 GEL A TINSUB 15 /cELLULosE NITRATE 12 ./-HYDROLIZED PoL YV1NYL- 10 ACE TA TE 11TRACING CLOTH 14 HYDR oLIzED POL YVIN YL- 1 7 ACE TA TE CELL ULOSE NJTRATE CELL ULOSE ACE TA TE F1 q. E.'

Z'INULl SION GELA TIN S UB CELL ULOSE NITRA TE' HYDROLIZED POL YVINYLACETATE CL O TH HYDROLIZED POLYVINYLACETA TE CELLULOSE NITRATE GELA TIN SUBGELA TIN CARL. F. SMITH INVENTOR.

ATTORNEYS Patented Feb. 23, A1954 l UNITEDy STATES PATENT-- 2,670,288 nPHOT'UGRBHIC TRAQG @om "f .l om' Esmee, menester, N. Y., assigner toEase..

man Kodak Company, Rochester, N. Y., a corporation ol!4 New JerseyApplication November so, 1951, serial No. 259,189

(ci. iis-8i 4 Claims. .1

This invention relates to photographic tracing cloth and moreparticularly to a photographic tracing cloth structure which hassubstantially improved light transmission without impairment of otherdesirable characteristics'. l

As is Well understood, photographic tracing cloth is employed, forexample, by being exposed to a drawing, or a negative' thereof,'t`oforinan image on the tracing'cl'o'th. Afterproper process'- ing, thetracing cloth may then be employed to print the image ontoI ablue printor other similar copying paper, or the like.

In general, photographic tracing cloth consists of a sheet of sizedcloth which is Waterproofed on both sidesto prevent aqueousphotographicsolutions rom attacking the sizing of the cloth. a photographic lightsensitive layer being coated over one or both of the waterproong layers.Heretofore, the waterproong layer' usually has consisted of a cellulosicmaterial, such as cellulose nitrate, Which material does notV properlyadhere to a starch-sized' cloth' withoutv the application of someintermediate subbing' material; When the tracing cloth, after exposure,is treated in aqueous photographic processing solutions even when asubbing material is employed, the waterproofing v layer may' come loose`and permit the water to reach and swell thestarclr sizing of the cloth,thereby making the drawing or tracing on the tracing cloth of no value.Another objection to tracing cloth which is made in this Way' is' thatafter photographic processing' andi drying ofthe material, thewaterproofing layerand its; emulsion sometimes peel or stripfrom thecloth basar f In the Nadeau and' Couch Patent 2,117,814 of May 17, 1938,these diiiiculties are overcome by employing a layer of a mixture ofgelatin and cellulose nitrate to the cloth base before the applicationof the waterproofing, the subbing and photographic emulsion layers.

While photographic tracing cloth made in accordance with this patent isvery satisfactory, I have found that it has two undesirable features. Ithas a rather poor light transmission which results in a low printingspeed and on prolonged immersion in aqueous liquids there is a tendencyof the Waterproofing layers to curl up and leave the edge of the cloth.

An object, therefore, of the present invention is an improvedphotographic tracing cloth which includes the desirable features of thetracing cloth described in Patent 2,117,814 and which also has superiorlight transmission and resistance to aqueous methods.

In accordance with the invention, these and replacing the cellulosenitrateI gelatin subbing layers of Patent 2,117,814 with subbingi layerscomprising a hydrolyzed polyvinyl acetatey containing from 27 to401%.v'inyl acetate. I have found that by employing thesev hydrolyzedpolyvinyl acetate layers, the printing speed of the finished product isincreased approxirnatelyy 30% and the'edge curl is substantiallyeliminated. The hydrolyzed polyvinyl acetate kcontaining 27% vinylacetate is preferred; l

My invention Will be 'further understood by reference to the drawing inwhich; Fig. 1 is aview in section of one form off atracing cloth madeinaccordance with [my invention which, except for the novel use ofhydrolyzed polyvinyl acetate layers, is similar instructure to that. of4Patent 2,117,814; and Fig, "21s' a.y quite. similar structure having,however, .a, gelatin coating inthe place of the cellulose` acetate,coating; of Fig.v 1.

In making the photographic `tracing cloth shown in liig. l, a4 solutionvofrntlie hydrolyzed polyvinyl acetate is applied to both. sides of acalendered, starch-sized-l cloth base. After this solution is dried asolutionofcellul'ose nitrate is applied over both hydrolyzed polyvinylacetate layers and permitted to dry. n one side'ofthe element thusformed a thin` layer of.A gelatin is' applied and over'this layer.iscoated the light sensitive photographic emulsion.- If the tracingcloth structure shown in Fig. 1` desired, the cellulose' nitrate .layeron. the side opposite the emulsion side may;- be' overcoated withfcellulose acetate; or, if. the structure showneinlFig. 2- is.desired',.,then,instead of the acetate layer a mixed gelatin-cellulosenitrate layer mayk be used over which anr anti-hala'ti'on gelatincoating is placed. The structure of my improved vtracingl cloth mayfurther be apparent by reference to the drawing. In Fig. 1 of thedrawing I0 represents a calendered starch-sized tracing cloth. On thiscloth base are coated layers ll and l2 of the selected hydrolyzedpolyvinyl acetate. The following solution is typical of the one whichmay be advantageously employed.

Percent Hydrolyzed polyvinyl acetate (27% vinyl acetate) 2 Water 20Methyl Cellosolve 15 Methyl alcohol 63 other objects may be attained, Ihave found. by u nitrate.

A suitable composition for the solution employed to coat this layer isthe following:

These layers are dried and on one of them is laid a thin gelatin layerI5 which may be coated from the following solution:

Percent Gelatin 1.0 Acetic acid 1.0 v Water 5.0 Methyl alcohol 70.0Acetone 23.0

The gelatin layer is dried vsomewhat and over it is laid an ordinarygelatine-silver halide emulsion I6.

On the opposite side of the element formed by the application of theselayers to the cloth support l0, a layer H of any suitable backingmaterial, such as cellulose acetate.' is coated over the cellulosenitrate layer I4. The cellulose acetate employed may be hydrolyzedcellulose acetate of a precipitation value of 70% and may be coated froman acetone solution. i

Other cellulose organic acid esters such as cellulose acetate propionatecould be employed in place of the cellulose acetate layer shown as i1 inthe drawing. In making the photographic tracing cloth shown in Fig. 2, aprocedure, in general, similar to that employed for making the tracingcloth of Fig. 1 may be followed. A solution of the hydrolyzed polyvinylacetate is applied to both sides of the calendered, starch-sized clothbase 20. The resulting layers are shown respectively at 2l and 22 on thedrawing. After these layers are dried, a solution of cellulose nitrateis applied over both hydrolyzed polyvinyl acetate layers 2l and 22 toform nitrate layers 23 and 24. These nitrate layers are dried and coatedwith a gelatin subbing coating to produce layers 25 and 2l which aredried. On gelatin layer 25 is coated a light sensitive photographicemulsion 26 as by standard methods. On the opposite layer an additionalgelatin layer 28 is coated which prevents curling of the tracing clothand serves also as an anti-halation layer. The coating compositionsemployed in connection with the tracing cloth shown in Fig. 1 aresatisfactory for employment in making the tracing cloth of Fig. 2.

It is to be understood that this invention is not limited to the exacttype of sensitive tracing cloth and the sequence of layers described inthe above specification. For example, the support may be any type ofsuitable cloth or paper which has been sized with materials that swellor dissolve in Water. Other materials may be employed for thewaterproofing layer and additional layers of other material may beapplied to improve the dry and wet stripping characteristics of theiinished element. I contemplate the use of all modications andequivalents coming within the scope of the vappended claims. The variouslayers may be coated by any suitable methods known in the art.

I claim: Y

l. A photographic tracing cloth having improved light transmissioncomprising a sized cloth Base, a layer of hydrolyzed polyvinyl acetatehaving a vinyl acetate content ci 27 to 40% on each side of the clothbase, a separate layer of cellulose nitrate over each of the hydrolyzedpolyvinyl acetate layers, a silver halide emulsion layer attached to oneof the cellulose nitrate layers by a gelatin layer, and a celluloseacetate layer over the other of said cellulose nitrate layers.

2. The tracing cloth of claim 1 in which the polyvinyl acetate has avinyl acetate content of 3. A photographic tracing cloth having improvedlight transmission comprising a sized cloth base, a layer of hydrolyzedpolyvinyl acetate having a vinyl acetate content of 27 to 40% ony eachside of the cloth base, a separate layer of cellulose nitrate over eachof the hydrolyzed po1yvinyl acetate layers, a silver halide emulsionlayer attached to one of the cellulose nitrate layers, and a gelatinlayerover the other of said cellulose nitrate layers.

4. The tracing cloth of claim. 3 in which the polyvinyl acetate has avinyl acetate content of 27%.

CARL F. SMITH.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 2,117,814 Nadeau et al. May 17, 1938 2,135,524 Nadeau Nov. 8,1938 2,143,791 Nadeau Jan. 10, 1939 2,350,124 Nadeau et al. May 30, 19442,363,764 White Nov. 28, 1944

1. A PHOTOGRAPHIC TRACING CLOTH HAVING IMPROVED LIGHT TRANSMISSIONCOMPRISING A SIZED CLOTH BASE, A LAYER OF HYDROLYZED POLYVINYL ACETATEHAVING A VINYL ACETATE CONTENT OF 27 TO 40% ON EACH SIDE OF THE CLOTHBASE, A SEPARATE LAYER OF CELLULOSE NITRATE OVER EACH OF THE HYDROLYZED